Rec. ITU-T Q.703 (03/1993) � SIGNALLING SYSTEM No. 7 � SIGNALLING LINK
FOREWORD
CONTENTS
1 General
    1.1 Introduction
    1.2 Signal unit delimitation and alignment
    1.3 Error detection
    1.4 Error correction
    1.5 Initial alignment
    1.6 Signalling link error monitoring
    1.7 Link state control functions
    1.8 Flow control
2 Basic signal unit format
    2.1 General
    2.2 Signal unit format
    2.3 Function and codes of the signal unit fields
    2.4 Order of bit transmission
3 Signal unit delimitation
    3.1 Flags
    3.2 Zero insertion and deletion
4 Acceptance procedure
    4.1 Acceptance of alignment
    4.2 Error detection
5 Basic error correction method
    5.1 General
    5.2 Acknowledgements (positive acknowledgement and negative acknowledgement)
    5.3 Retransmission
6 Error correction by preventive cyclic retransmission
    6.1 General
    6.2 Acknowledgements
    6.3 Preventive cyclic retransmission
    6.4 Forced retransmission
7 Initial alignment procedure
    7.1 General
    7.2 Initial alignment status indications
    7.3 Initial alignment procedure
    7.4 Proving periods
8 Processor outage
9 Level 2 flow control
    9.1 General
    9.2 Detection of congestion
    9.3 Procedure in the congestion situation
    9.4 Congestion abatement procedure
10 Signalling link error monitoring
    10.1 General
    10.2 Signal unit error rate monitor
    10.3 Alignment error rate monitor
11 Level 2 codes and priorities
    11.1 Link status signal unit
    11.2 Transmission priorities within level 2
12 State transition diagrams, abbreviations and timers
    12.2 Abbreviations
    12.3 Timers